Surface-Enhanced Raman Spectroscopic Studies of Dissociative Adsorption of Amino Acids on Platinum and Gold Electrodes in Alkaline Solutions

Abstract

The dissociative adsorption of amino acids on Pt and Au electrodes in 0.1 M NaOH solutions was studied by cyclic voltammetry and surface-enhanced Raman spectroscopy (SERS). The intermediate species has been determined as adsorbed cyanide, which is designated by a potential-dependent vibration band around 2110 cm-1 on both Pt and Au surfaces. The dissociation of glycine can be observed on Pt surface in a wide potential region to form cyanide, while the dissociation of serine and threonine occurs at relatively high potentials along with the oxidation of their functional groups. The onset potential of dissociation of amino acids on the Pt surface increases in the order glycine < threonine < serine. It has been revealed that the self-inhibition of amino acid oxidation is originated from the strongly adsorbed cyanide, which is oxidized at potentials above 0.2 V vs SCE. On gold surfaces, cyanide species can be formed only from anodic oxidation of amino acids. The present study reveals characteristic interaction...